Integrated: Merge bworld

[Chen Liang]

Merge fixes necessary for API previewing

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Commit messages:
 - Merge branch 'bworld' of https://github.com/openjdk/valhalla into bworld-apis-merge
 - Merge bworld
 - Support preview features in libraries

The merge commit only contains trivial merges, so no merge-specific webrevs have been generated.

Changes: https://git.openjdk.org/valhalla/pull/2082/files
  Stats: 26 lines in 10 files changed: 8 ins; 2 del; 16 mod
  Patch: https://git.openjdk.org/valhalla/pull/2082.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/2082/head:pull/2082

PR: https://git.openjdk.org/valhalla/pull/2082